Radio Frequency Identification (RFID) is a non-contact automatic identification technology utilizing radio communication, which includes two main parts, i.e., an electronic tag and a reader. Non-contact data transmission is performed between the tag attached with codes and the reader through an antenna to realize an automatic identification process over a certain distance. In accordance with frequency bands, the current radio frequency identification systems may be divided into low-frequency systems (30˜300 KHz), high-frequency systems (3˜30 MHz) and ultra-high-frequency and microwave systems (300 MHz˜3 GHz or greater than 33 GHz). As a basis for a fast, real-time and accurate information acquisition and processing high tech and standardization of messages, RFID has been known in worldwide as one of top ten most significant technology in this century. Because of the gradually matured standardization of the UHF frequency band in China, and requirements for applications such as logistics, smart transport and digital tourism, the share of UHF frequency band products in the market of the RID industry keeps increasing. RFID tag antennas and reader antennas, as an important communication tool, play significant roles in identification systems. In order to quickly read information on the tag over a long distance, systems with high frequency band attract more attention. Since a RFID tag antenna is the most variable part in a RFID system and the design thereof needs to meet the practical requirements of miniaturization, conformality, low cost and low loss, it is important for the whole RFID system to optimize the design thereof.
At present, bandwidths of RFID tag antennas used in various regions are inconsistent with each other in the high-frequency ranges thereof. For example, a band of 866˜868 MHz is employed in the Europe, and a band of 902˜928 MHz is employed in the United States. When the RFID tag antenna is switched between the different bandwidths in the above different regions, the conventional RFID tag antenna is very difficult to be identified in the regions with different bandwidths due to bandwidth limitations. Moreover, a resonant frequency is lower than 910 MHz according the conventional RFID tag antennas, so that a reading distance is significantly poor. In order to achieve a good identification effect, it is necessary to increase the thickness, the length and the width of the conventional RFID tag antenna, which results that an outline dimension of the RFID tag antenna is increased and costs are increased accordingly.
Therefore, a novel RFID tag antenna with ultra-thin dual-frequency micro strip patch antenna array, which has compatibility and is capable of identification over a long distance, becomes a development direction for production in this field.